I can't make my JTextArea Scrollable

I am supposed to display data from a file into a JTextArea.
To make it scrollable, I put it into a JScrollPane, but as soon as I input the data read from the file into JTextArea, the text goes out of bounds.
If i don't put anything in the JTextArea, and enter text from keyboard, it remains scrollable, but if I set text read from a file, it's scroll doesn't work.